The Women’s Sports Foundation Report Brief: Her Life Depends On It III & Female Athletes and Knee Injuries

For an athlete, there is a sound that they hope never to hear.

That sound, often described as a “pop,” signals that the athlete

may likely have torn an anterior cruciate ligament (ACL), a

ligament that serves as a key stabilizer for the knee. As more

and more athletes at all ages have entered the competitive

arena and found their way into recreational sport programs,

there has been an increase in the public understanding of knee

injuries. And there is reason for concern.

In general, irrespective of gender, ACL injuries account for

50% or more of all knee injuries (Joseph et al., 2013) and have

been described as the “largest single problem in orthopaedic

sports medicine” (Renstrom et al., 2008). Knee injuries also

are among the most economically costly of sports injuries,

frequently requiring expensive surgery and rehabilitation

(Joseph et al., 2013). However, the overall incidence of ACL

injuries is low, occurs more frequently in men’s sports, and

constitutes approximately 3% of all injuries in the NCAA sample

(Hootman, Dick & Agel, 2007).

For female athletes, who do tend to be more vulnerable to

ACL tears and ruptures, the problem of knee injuries has been

described as an “epidemic.” While it is the case that female

athletes do experience knee injuries at higher rates than their

male counterparts in some sports, sometimes being four to six

times more likely to experience a knee injury, understanding

the gendered dynamics around knee injuries helps to put what

this increased vulnerability means – and what it doesn’t mean –

into perspective.

The manner in which injuries occur in male and female athletes

is often represented differently in the media. While data does

support that female athletes are more vulnerable to ACL

injuries, there is almost no discussion in contrast regarding

the fact that NCAA male soccer players are 64% more likely

to experience hamstring injuries compared to female soccer

players (Cross, Gurka, Saliba, Conaway, & Hertel, 2013).

There has been no news account that has viewed the higher

incidence of hamstring injuries among male soccer players

as being epidemic in proportions. Thus, the challenge is

sorting through the reasons why female athletes may be more

vulnerable to ACL tears.

And some of those reasons are social. The most recent

FIFA Women’s World Cup in 2015, which was held in venues

across Canada, provides further insight into the gendered

dynamic that affects incidence of injury. According to NCAA

research, playing surface affects incidence of knee injury. In

a study looking at the incidence of ACL tears among college

football players, “The rate of ACL injury on artificial surfaces

is 1.39 times higher than the injury rate on grass surfaces.

Non-contact injuries occurred more frequently on artificial turf

surfaces (44.29%) than on natural grass (36.12%).” In the case

of the FIFA Women’s World Cup, contrary to the Men’s World

Cup, which has historically been played on grass fields, and

despite international protests, the women’s games would be

played in venues with artificial turf.

Based on research, there are other reasons, stemming from

hormonal and biomechanical sources, which contribute to

the incidence of knee injuries in female athletes. To follow

are highlights from some of the most recent research on

the subject. updated 9.19.16

IncidenceA variety of analyses of the NCAA data highlight the rates of

ACL injuries among women athletes with particular attention

paid to gender differences in basketball and soccer, sports

in which the rules of play are largely the same for men and

women, and thus gender comparisons are thought to be

especially meaningful.

• Over a 16-year period, from 1988-89 to 2003-04, the

rate of ACL injuries was .07 for men and .23 for women

in basketball and was .09 for men and .28 for women

in soccer. Both the rate of ACL injuries among women

athletes and the gender gap remained stable over this

period (Hootman et al., 2007).

• The NCAA data also showed that three of the four sports

with the highest rates of ACL injuries were women’s sports

(gymnastics, basketball, and soccer). The fourth sport

with a high rate of this injury is spring football. All had

significantly higher ACL injury rates than any other sport

(Hootman et al., 2007).

• An analysis of ACL injury rates in a sample of U.S. high

schools found that, overall, girls and boys had similar rates

of ACL injuries, and, consistent with the NCAA data, the

sports with the highest rates were football, girls’ soccer,

and girls’ basketball (Joseph et al., 2013).

• An expanding body of research, employing different

measures and samples from different countries provides

further support for the finding that females have higher

rates of ACL injuries than males when exposed to the same

sport (Moses, Orchard & Orchard, 2012).

• Gender differences in the incidence of ACL injuries occur

after the onset of puberty (Hewett, Myer, Ford, Paterno &

Quatman, 2012).

• While research and commentary continues to focus on

gender differences in rates, leading to a common belief

that ACL injuries are a problem particular to women

athletes, it is important to note that the highest incidence,

that is number of ACL injuries, occurs in men’s sports.

Both the early analyses of collegiate athletes by Hootman,

Dick & Agel (2007) and the more recent high school data

reported by Joseph et al. (2013) indicate that football had

the highest number of ACL injuries.

Mechanisms of ACL InjuriesResearch consistently demonstrates that the majority of ACL

tears among women athletes are non-contact, that is to say,

the forces applied to the knee at the time of injury were a result

of the athlete’s movements, not contact with another athlete or

object (Shultz, 2008; Arendt, 2007).

• Typically, these injuries occur during planting, cutting, and

landing maneuvers (Giugliano & Solomon, 2007).

The occurrence of a high proportion of ACL injuries through

non-contact mechanisms is significant, as it points to features

of the athlete’s movement and not the circumstances of the

sport activity as the precipitating event for the injury.

This presents possibilities for prevention through training to

alter movement patterns. Accordingly, recent research has

concentrated extensively on identifying and understanding the

mechanisms whereby risk factors operate and following from

this, prevention strategies that are based on understanding risk

factors and mechanisms.

Risk FactorsInvestigations employing different techniques, most notably

video analysis, have identified gender differences in movement

patterns that place athletes at risk for ACL tears. While these

patterns are not exclusive to women, research suggests

that females perform riskier neuromuscular patterns more

often than men when doing similar sporting moves (Arendt,

2007; McLean, 2008). A variety of factors have been studied

to determine why females are more at risk than males for

sustaining a non-contact ACL injury.

The most extensive research has been directed to landing

techniques and neuromuscular recruitment patterns, as well

as anatomical and hormonal influences. Notable about these is

that the first two offer the greatest potential for modification

through training programs, whereas the anatomical and

hormonal influences are largely not modifiable.

• Research on neuromuscular and biomechanical factors

has examined factors such as muscle activation, strength,

balance, control, and lower-extremity biomechanics.

Deficiencies in these factors may leave athletes more

susceptible to the knee motions that are considered

mechanisms of ACL injury (Hewett et al., 2012).

Women’s Sports Foundation

www.WomensSportsFoundation.org • www.SHENetwork.org • Follow the Women’s Sports Foundation on:

• Research on anatomical factors has concerned knee

geometry and alignment. Hormonal research has been

directed to determine the influence of hormonal variations

associated with menstrual cycle phase (Smith et al., 2012,

part 1). There is also preliminary evidence of genetic

influences on familial disposition to ACL injuries (Hewett et

al., 2012; Smith et al., 2012, part 2). Research advances in

these areas may enable the identification of individuals at

higher risk, who may be targeted for interventions (Hewett

et al., 2012).

• External risk factors, that is those external to the athlete,

that have been identified for ACL injuries relate to shoe

surface interaction and include weather, playing surface,

and footwear (Smith et al., 2012, part 2). These factors may

interact with those that are gender-related.

• Individuals who have sustained an ACL injury are at high

risk for a subsequent ACL injury (Shultz et al, 2012; Smith

et al., 2012, part 2).

• There is consensus that the causes of ACL injuries are

multifactorial and risk factors operate in combination

(Shultz et al., 2012).

PreventionThe main development in research on ACL injuries since the

previous version of this report was issued is the growing

attention to research on prevention and the accumulating

evidence on the components of successful interventions to

reduce the incidence of ACL injuries.

• Prevention programs concentrate on reducing

neuromuscular deficits that increase the incidence of ACL

injury, and there is evidence that neuromuscular training

reduces the level of risk factors (Hewett et al., 2012).

• Successful training programs involve extensive training

volumes and time commitment on the part of athletes and

coaches. These can deter the implementation of successful

interventions (Hewett et al., 2012).

• Research in Norway on the reduction of ACL injuries in

team handball provides evidence of the importance of

a comprehensive approach to injury prevention. Results

from the Norwegian experience emphasize the importance

of educational initiatives to promote the importance of

injury prevention and reinforce the importance of support

and involvement by coaches and team and club officials

(Myklebust, Skølberg & Bahr, 2013).

• There is growing recognition of the importance of the

timing of prevention initiatives. The emergence of gender

differences in joint laxity and neuromuscular control during

maturation, coupled with a divergence in the incidence

of injuries after puberty, indicates that injury prevention

efforts should be introduced in preadolescence or early

puberty (Hewett et al., 2012).

Future Research and Actions NeededWhile there is evidence of the success of training programs

to reduce the incidence of ACL injuries, research is needed

to understand more clearly the elements of the programs

that contribute to injury reduction, in order to improve their

efficiency and effectiveness.

Publicizing the importance of interventions to reduce injuries

and to gain the support of coaches and team and club officials

could help to ensure compliance with training programs.

There also is a need to identify barriers and facilitators

to maximize acceptance, compliance, and retention of

community-based interventions to reduce ACL injuries (Shultz

et al., 2012).

Adapted from Staurowsky, E. J., DeSousa, M. J., Miller, K.

E., Sabo, D., Shakib, S., Theberge, N., Veliz, P., Weaver, A., &

Williams, N. (2015). Her Life Depends On It III: Sport, Physical

Activity, and the Health and Well-Being of American Girls and

Women. East Meadow, NY: Women’s Sports Foundation.

The full report can be accessed online at:

www.WomensSportsFoundation.org/HerLifeDependsOnIt3

Women’s Sports Foundation

www.WomensSportsFoundation.org • www.SHENetwork.org • Follow the Women’s Sports Foundation on:

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